1. Field of the Invention
The present invention relates to a method of forming color photographic images, and more particularly to a method of forming color photographic images using a novel yellow color forming coupler. The present invention also relates to a color photographic light sensitive element containing the novel yellow color forming coupler.
2. Description of the Prior Art
It is well known that color forming couplers couple with oxidation products of primary aromatic amino developing agents to form color photographic images. Most conventional yellow color forming couplers are four-equivalent couplers and these couplers require four moles of exposed silver halide as oxidizing agents to form one mole of azomethine dye. An introduction of a large amount of silver halide into light-sensitive layers leads to some disadvantages such as an increase in light scattering in the emulsion layers and consequently, a decrease in the sharpness of the images formed, and in addition, an increase in processing time for the light-sensitive materials due to an increase in thickness of the emulsion layers. Furthermore, the formation of dyes with these couplers is not completed during color development and thus it is necessary to use strong oxidizing agents in subsequent processing steps to complete the dye formation.
In order to improve these defects, two-equivalent yellow color forming couplers have been provided, which require only two moles of exposed silver halide to form one mole of azomethine dye.
The two-equivalent yellow color forming couplers have, in general, chemical structures in which one of the hydrogen atoms of the active methylene group is substituted with an atom or group releasable on coupling. Examples of such atoms or groups releasable on coupling are a fluorine atom as described in U.S. Pat. No. 3,277,155, a phenoxy group as described in U.S. Pat. No. 3,408,194, an acyloxy group as described in U.S. Pat. No. 3,447,928, a sulfoxy group as described in U.S. Pat. No. 3,415,652, and a group having a saccharin structure as described in German patent application Laid Open No. 2,057,941.
However, these couplers are not sufficient for use in color photography because they are accompanied by disadvantages in that the coupling reactivity is insufficient, in that a marked color fog is produced, in that the couplers per se are unstable and their coupling activities decrease or in that color stain occurs in the light-sensitive materials during storage, in that the yellow color images formed are unstable or in that the preparation of the couplers is quite difficult.
Couplers which improve these defects are yellow color forming couplers having a coupling releasable group derived from imide compounds as described in U.S. patent application Ser. Nos. 235,937, filed on Mar. 20, 1972 and 319,806, filed on Dec. 29, 1972 and Japanese patent application Laid Open No. 29432/73.
However, the couplers described in these patent specifications have an insufficient solubility in a coupler solvent and thus many difficulties are encountered in the manufacture of color photographic light-sensitive materials containing these couplers in that specific attention is required during preparation and storage of the coupler dispersion, in that the couplers crystallize in the coupler dispersion and they tend to promote uneven coating of emulsion layers resulting in a decrease in photographic properties of the layers. Therefore, development of two-equivalent yellow color forming couplers which have a good dispersion property and with which coating defects do not occur has been desired.